Since the clinical use of nitrogen mustard as an anticancer agent in the 1940s for the first time in the world, numerous anticancer drugs have ever been developed. Actually, for example, antimetabolites such as 5-fluorouracil, antitumor antibiotics such as adriamycin, platinum complex such as cisplatin, and plant-derived carcinostatics such as vindesine have been subjected to clinical use.
However, most of these carcinostatics have significant side effects such as digestive disorders, myelosuppression and alopecia since they are cytotoxic also to normal cells. Due to the side effects, their range of application is limited, and further, the therapeutic effects themselves are partial and short, in most cases.
In addition to the therapeutic effects and the side effects, metabolic stability is one of important requirements for a drug since pharmacokinetics of a drug in a human body is greatly affected by susceptibility to metabolism. Further, storage stability of a pharmaceutically active ingredient contained in a drug is important for commercial use thereof. Therefore, it is important to evaluate the metabolic stability and the storage stability of a drug candidate.
Developments of new carcinostatics have been made; however, satisfactory results have not yet been obtained. Patent Documents 1, 2 and 3 disclose certain kinds of compounds having fibrosing inhibitory action, antitumor action and STAT3/5 activation inhibitory action, respectively. However, the compounds specifically disclosed in the present application are different from those specifically disclosed in these Patent Documents and it is not known whether the compounds of the present application have antitumor actions.